Exercise Triggers Memory-Related ‘Brain Ripples’, Study Finds : ScienceAlert

Exercise works wonders throughout the human body, including the brain.

Research suggests an array of neurological benefits, such as reducing the brain’s biological age, enhancing learning and memory, and protecting against dementia.

Now, a new study offers one of the clearest glimpses yet into a suspected mechanism: after a single 20-minute session of light-to-moderate cycling, people showed changes in memory-linked brain activity.

A hippocampal sharp wave-ripple begins with highly synchronized patterns of neuronal activity in the hippocampus, a brain region with important roles in memory. These signals then travel elsewhere in the brain, affecting much of the cortex as well as some subcortical areas.

Much of what we know about these ripples comes from animal and human studies that used implants to measure brain activity.

But measuring sudden changes in brain activity shortly after exercise is a harder task, one usually done with brain imaging scans that can only hint at ways exercise may boost brain function – detecting, for example, more oxygenated blood.

In this new study, an international team of researchers looked at the brain activity of 14 epilepsy patients who had electrodes implanted in their brains “solely on the basis of clinical requirements, as determined by a team of epileptologists and neurosurgeons,” they explain.

The study provides the “first direct evidence” of hippocampal ripples in human brains after physical activity, the authors report.

This offered a rare view of neuron activity from inside human brains after exercise, explains senior author Michelle Voss, a cognitive neuroscientist at the University of Iowa.

“We’ve known for years that physical exercise is often good for cognitive functions like memory, and this benefit is associated with changes in brain health, largely from behavioral studies and noninvasive brain imaging,” Voss says.

“By directly recording brain activity, our study shows, for the first time in humans, that even a single bout of exercise can rapidly alter the neural rhythms and brain networks involved in memory and cognitive function.”

The study participants, who ranged in age from 17 to 50 years old, all had drug-resistant epilepsy and were undergoing pre-surgical evaluation.

Electrodes implanted in their brains allowed researchers to record intracranial electroencephalographic (iEEG) data, which are useful for epilepsy treatment and can also help illuminate brain phenomena such as hippocampal ripples.

After warming up, participants exercised on a stationary bike for 20 minutes at a pace they thought they could maintain the whole time. The iEEG data captured their brain activity before and after this session, revealing a rarely seen picture of how exercise might fortify brain function.

Exercise led to an elevated ripple rate in the hippocampus. It also strengthened the connectivity between hippocampus ripples and activity elsewhere in the brain: in the limbic system and default mode network (DMN).

This occurred after just one session of light-to-moderate exercise, resulting in significantly different ripple dynamics between the hippocampus and cortex, and mirroring findings from previous brain imaging studies.

The study also found a link between higher exercise intensity – as measured by heart rate during exercise – and greater enhancement of ripple dynamics in specific neural networks, like the DMN, while resting after exercise.

Despite its relatively small sample, the study provides a rare glimpse inside human brains after exercise, yielding valuable insights that likely apply to people with or without epilepsy, the researchers say.

“The patterns we see after exercise closely match what’s been observed in healthy adults using noninvasive brain imaging,” Voss says.

“That convergence across very different methods is one of the strongest indicators that the effects are not specific to epilepsy but reflect a more general human brain response to exercise.”

The study was published in Brain Communications.